1. Field of the Invention
This invention relates to a method for producing a fuel coal, more particularly to a method for producing a bio-coal.
2. Description of the Related Art
Nowadays, large amounts of fuel coal are being consumed by power generation boilers in steel mills and certain large factories. However, combustion of fuel coal causes global warming owing to massive emission of greenhouse gases such as carbon dioxide. With the rising concerns over environmental issues, replacing fossil fuels with green energy and therefore reducing carbon dioxide emission has become an important topic.
A common type of green energy is biomass. Plants and cash crops, such as miscanthus, willow, millet, hemp, corn, sugarcane, palm tree, and the like, are transformed into fuels. The simplest way is, for example, direct combustion of the biomass to obtain thermal energy. Plants absorb and transform carbon dioxide into organic substances. The organic substances are released back to the atmosphere as carbon dioxide after the plants are oxidized (for example, combusted). Therefore, by using biomass as fuel, carbon dioxide content in the atmosphere can be balanced which is helpful for reducing the greenhouse effect. Moreover, this absorption and release of carbon oxide is a rather faster cycle. Also, the plants as fuel can be grown rapidly and repeatedly.
However, energy released during combustion of untreated plant fiber is less than energy released during combustion of fossil fuels. The energy contained in a substance is defined as calorific value which has a unit of energy per unit mass, such as cal/g. The untreated plant fiber also tends to rot after absorbing moisture in the atmosphere which makes it inconvenient to store and transport.
There remains a need for developing a technique for mass transformation of plant fiber into bio-coal.
Palm tree is a kind of high value cash crop being extensively planted in Southeast Asia where a large number of oil palms are grown. Fruits and kernels in the oil palms have rich oil content. Oil is extracted from the oil palms and then is processed into well-known palm oil. Fiber residue of extracted palm fruits is usually discarded or used as ash fertilizer after combustion, and thus has less utility value.
Therefore, this invention provides a method for producing a bio-coal from the widely available fiber reside of oil palm fruit. The bio-coal is able to satisfy the need for extensive fuel supplement in power generation boilers of large factories.